如何在WPF中将ObservableCollection与Listbox绑定

Question

I would like to bind ObservableCollection with Listbox in WPF application. So when elements in the ObservableCollection will be modified the ListBox will update itself.

There is a public static ObservableCollection<Camera> extension = new ObservableCollection<Camera>(); in class Camera

And the ListBox is in the class MainWindow.xaml

I tried that, but it does not work:

Camera class:

       using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;

namespace HomeSecurity {

    public class Camera : INotifyPropertyChanged {
        public static readonly Regex AxisMacPattern = new Regex("00408[Cc][a-zA-Z0-9]{6}");
        public string _IP;
        public string IP {
            get {
                return _IP;
            }
            set {

                if (_IP != value) {
                    _IP = value;
                    OnPropertyChanged("IP");
                }

            }
        }
        public string _HTTPPort;
        public string HTTPPort {
            get {
                return _HTTPPort;
            }
            set {

                if (_HTTPPort != value) {
                    _HTTPPort = value;
                    OnPropertyChanged("HTTP");
                }

            }
        }
        public string _MAC;
        public string MAC {
            get {
                return _MAC;
            }
            set {

                if (_MAC != value) {
                    _MAC = value;
                    OnPropertyChanged("MAC");
                }

            }
        }
        public string _ServiceName;
        public string ServiceName {
            get {
                return _ServiceName;
            }
            set {

                if (_ServiceName != value) {
                    _ServiceName = value;
                    OnPropertyChanged("ServiceName");
                }

            }
        }
        public string _FullName;
        public string FullName {
            get {
                return _FullName;
            }
            set {

                if (_FullName != value) {
                    _FullName = value;
                    OnPropertyChanged("FullName");
                }

            }
        }
        public string _HostName;
        public string HostName {
            get {
                return _HostName;
            }
            set {

                if (_HostName != value) {
                    _HostName = value;
                    OnPropertyChanged("HostName");
                }

            }
        } 

        public Camera() { }
        public Camera(string MAC) : this(null, null, MAC, null, null, null) { }
        public Camera(string MAC, string ServiceName) : this(null, null, MAC, ServiceName, null, null) { }
        public Camera(string IP, string HTTPPort, string MAC, string ServiceName, string FullName, string HostName) {
            this.IP = IP;
            this.HTTPPort = HTTPPort;
            this.MAC = MAC;
            this.ServiceName = ServiceName;
            this.FullName = FullName;
            this.HostName = HostName;
            AddToExtension(this);
        }
        public static ObservableCollection<Camera> _extension = new ObservableCollection<Camera>();
        //

        public ObservableCollection<Camera> extension {
            get { return _extension; }
            set {
                if (_extension != value) {
                    _extension = value;
                    OnPropertyChanged("extension");
                }

            }
        }
        private void OnPropertyChanged(string propertyName) {
            PropertyChangedEventHandler handler = PropertyChanged;
            if (handler != null) {
                handler(this, new PropertyChangedEventArgs(propertyName));
            }
        }
        #region INotifyPropertyChanged Members

        public event PropertyChangedEventHandler PropertyChanged;

        #endregion


        // 

        public static void AddToExtension(Camera camera) {
            _extension.Add(camera);
        }

        public static void RemoveFromExtension(Camera camera) {
            _extension.Remove(camera);
        }

        public static Camera GetFromExtension(String MAC) {
            foreach (Camera camera in _extension)
                if (camera.MAC.Equals(MAC))
                    return camera;
            return null;
        }

        public static void PrintExtension() {
            foreach (Camera camera in _extension)
                Console.WriteLine(camera);
        }

        public override string ToString() {
            return "IP: " + IP + " HTTP Port: " + HTTPPort + " MAC: " + MAC + " Service Name: " + ServiceName + " FullName: " + FullName + " HostName: " + HostName;
        }
    }
}

XAML:

  <Window x:Class="HomeSecurity.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local="clr-namespace:HomeSecurity" 
        Title="MainWindow" WindowState="Maximized" Loaded="Window_Loaded"

        >

    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="2*" />
            <RowDefinition Height="8*" />
        </Grid.RowDefinitions>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="*" />
            <ColumnDefinition Width="1366" />
        </Grid.ColumnDefinitions>
        <Border BorderBrush="Red" BorderThickness="4" Grid.Column="1" Grid.Row="0">
            <ListBox x:Name="CameraListBox"
         ItemsSource="{Binding Path=Camera.extension}">
                <ListBox.Resources>
                    <DataTemplate DataType="{x:Type local:Camera}">
                        <Border BorderBrush="Black" BorderThickness="1" CornerRadius="5">
                           <TextBox Text="Hello World" /> 
                        </Border>
                    </DataTemplate>
                </ListBox.Resources>
            </ListBox>
        </Border>

        <Border BorderBrush="Green" BorderThickness="2" Grid.Column="1" Grid.Row="1">
            <ScrollViewer >
                <WrapPanel x:Name="VideoPanel" >
                </WrapPanel>
            </ScrollViewer>
        </Border>


    </Grid>

</Window>

MainWindow.xaml.cs:

using Bonjour;

namespace HomeSecurity {
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window, INotifyPropertyChanged {

        public MainWindow() {
            DataContext = this;
            InitializeComponent();

        //   this.DataContext = this;
        }
       //
        private Camera _camera;
        public Camera Camera
        {
            get { return _camera; }
            set
            {
                if (_camera != value)
                {
                     _camera= value;
                     OnPropertyChanged("Camera");
                }

            }
        }

        /// <summary>
        /// Raises the PropertyChanged notification in a thread safe manner
        /// </summary>
        /// <param name="propertyName"></param>
        private void OnPropertyChanged(string propertyName)
        {
            PropertyChangedEventHandler handler = PropertyChanged;
            if (handler != null)
            {
                handler(this, new PropertyChangedEventArgs(propertyName));
            }
        }

        #region INotifyPropertyChanged Members

        public event PropertyChangedEventHandler PropertyChanged;

        #endregion
        //
        private void Window_Loaded(object sender, RoutedEventArgs e) {
            createGUI();
        }

        private void createGUI() {
            Console.WriteLine("dupa");
            Scanner.ScanService();
      //      startListening();
            //THIS CODE WON'T RUN BECAUSE   Scanner.ScanService(); have frozen it
            AddVideoStream("192.168.0.2");
            AddVideoStream("192.168.0.2");
            AddVideoStream("192.168.0.2");
        }

        private void startListening() {
            Camera._extension.CollectionChanged += (s, e) => {
             //  CameraListBox.Items.Add(Camera.extension.Last());
            };
        }


        //TEN
        private void AddVideoStream(String sourceIP) {
            int cols = 2;
            int formsHostWidth = (int)(VideoPanel.ActualWidth / cols) - 4;

            WindowsFormsHost formsHost = new WindowsFormsHost();
            VideoStream videoStream = new VideoStream(sourceIP);
            formsHost.Width = formsHostWidth;
            formsHost.Height = videoStream.GetPrefferedHeight(formsHostWidth);
            formsHost.Child = videoStream;
            Border lineBorder = new Border();
            lineBorder.BorderBrush = Brushes.Green;
            lineBorder.BorderThickness = new Thickness(2);
            lineBorder.Child = formsHost;
            VideoPanel.Children.Add(lineBorder);

        }
    }
}

If I change constructor in MAinWindow.xaml.cs to:

  InitializeComponent();
            Camera = new Camera();
            DataContext = this;

I get:

but this is not updated data... it is data frome the time where the Camera object was inserted in the extension.

Answer 1

Try to create a property that return extension static field, then bind your ListBox to that property. As far as I know you have to bind to property instead of field.

public static ObservableCollection<Camera> extension = new ObservableCollection<Camera>();
public ObservableCollection<Camera> bindableExtension 
{ 
    get { return extension; }
}

UPDATE :

As I can see from update you set DataContext to code behind. This means, you have to create a property named Camera in MainWindow.xaml.cs. Then you have to either implement INotifyPropertyChanged there or initialize Camera property before setting the DataContex :

public MainWindow() {
            InitializeComponent();
            this.Camera = new Camera();
            this.DataContext = this;
        }
...
public Camera Camera { get; set; }

Answer 2

You don't want to use a static property unless you really want to be shared between all instances of your class.

When your UI is initialized extension will be null. So the binding will be setup to null and nothing will happen. What you need to do is let your UI know when extention is updated, so it can listen for when new objects are added. Does that make sense?

Your example above, the property is not calling PropertyChangedEventArgs when extension is created so it is not actually listening to your collection.

public class Camera : INotifyPropertyChanged
{
        private ObservableCollection<Camera> _extension;
        public ObservableCollection<Camera> extension;
        {
            get { return _extension; }
            set
            {
                if (_extension != value)
                {
                     _extension= value;
                     OnPropertyChanged("extension");
                }

            }
        }

        /// <summary>
        /// Raises the PropertyChanged notification in a thread safe manner
        /// </summary>
        /// <param name="propertyName"></param>
        private void OnPropertyChanged(string propertyName)
        {
            PropertyChangedEventHandler handler = PropertyChanged;
            if (handler != null)
            {
                handler(this, new PropertyChangedEventArgs(propertyName));
            }
        }

        #region INotifyPropertyChanged Members

        public event PropertyChangedEventHandler PropertyChanged;

        #endregion

}

Also add this to your constructor DataContext = this , and implement INotifyPropertyChanged in your window class also. Something like this

public partial class MainWindow : Window, INotifyPropertyChanged
{
        public MainWindow() {
            DataContext = this;
            InitializeComponent();
        }

        // ... 

        private Camera _camera;
        public Camera Camera;
        {
            get { return _camera; }
            set
            {
                if (_camera != value)
                {
                     _camera= value;
                     OnPropertyChanged("Camera");
                }

            }
        }

        /// <summary>
        /// Raises the PropertyChanged notification in a thread safe manner
        /// </summary>
        /// <param name="propertyName"></param>
        private void OnPropertyChanged(string propertyName)
        {
            PropertyChangedEventHandler handler = PropertyChanged;
            if (handler != null)
            {
                handler(this, new PropertyChangedEventArgs(propertyName));
            }
        }

        #region INotifyPropertyChanged Members

        public event PropertyChangedEventHandler PropertyChanged;

        #endregion
}

I think you need to have a data template for something to show up too

<ListBox x:Name="CameraListBox"
         ItemsSource="{Binding Path=Camera.extension}">
    <ListBox.Resources>
        <DataTemplate DataType="{x:Type local:Camera}">
            <Border BorderBrush="Black" BorderThickness="1" CornerRadius="5">
                <TextBox Text="Hello World" />
            </Border>
        </DataTemplate>
    </ListBox.Resources>
</ListBox>